docs: def _get_default_mapping(self, obj):
          """Return default mapping if there are no special needs."""
          mapping = {v: k for k, v in obj.TYPE_MAPPING.items()}
          mapping.update({
              fields.Email: text_type,
              fields.Dict: dict,
              fields.Url: text_type,
              fields.List: list,
              fields.LocalDateTime: datetime.datetime,
              fields.Nested: '_from_nested_schema',
          })
          return mapping